The invention generally relates to machine tools, and in particular, to machine tools employing interchangeable pallets which are fixtured or registered on a pallet receiver base adjacent to the main machine base.
The interchange of pallets on a machine tool is well developed art, wherein pallets having a common machine registration surface may be employed to adapt workpieces to the machine. By the use of common pallets, a first workpiece may therefore be operated upon by a machine cutter while a second workpiece may be fixtured at a remote position from the machiine to a pallet for subsequent interchange with a finished workpiece. The interchange of workpiece pallets may be automatic by pallet interchangers or may be manual, carried out by an operator.
Final registration and location of the pallet with respect to the machine tool is of critical importance, and a variety of pallet locators have been employed in the prior art. One prior assembly utilized in U.S. Pat. No. 3,054,333 consists of a plurality of conical locating pins on a receiver base and a like plurality of mating conical sockets on the underface of a pallet, wherein a pallet is clamped down socket-to-pin by a clamp piston. The analogy may be made between the reference patent and other similar types of "shot pin" locators which inject a conical tapered pin into a cooperating socket to locate one member with respect to another. The problem inherent in utilizing such a mechanism for final registration of a pallet on a receiver base is that it is difficult to align the pins and sockets to level the pallet in a horizontal plane, and to locate the pins and sockets so they will not tend to fight one another for radial location with respect to the pin. Additionally, it can be appeciated that as inevitable wear occurs, in one or more pin-socket sets, the pallet will be tilted with respect to the horizontal plane and will tend to lose its alignment of the vertical stack of receiver base, pallet, and workpiece.
A second prior art pallet registration apparatus is disclosed in U.S. Pat. No. 3,543,392 in which the receiver base and the pallet underface are each fitted with one-half of a multitooth facial coupling each having a plurality of conforming teeth. The separable coupling halves tend to minimize and distribute wear around the coupling teeth which tends to maintain the accuracy of the stack height and level attitude of the pallet with respect to the machine tool, but the facial array is expensive to produce and it is difficult to produce pallet coupling halves which mate equally alike wih the receiver base coupling half.
Applicant has obviated the difficulties inherent in these types of prior art devices by a unique mechanism employing a pin and socket combination for alignment while utilizing stiff, rigid bearing surfaces for ultimate clamping and location of the pallet with respect to the receiver base.
It is therefore an object of the present invention to provide a pallet registration mechanism capable of accurately aligning a pallet with respect to a receiver base, yet providing a stiff location surface to withstand machining forces.
Another object of the present invention is to provide a pin and socket registration means capable of compensating for wear at the pin and socket interface.
A still further object of the present invention is to provide a pallet registration means capable of distributing wear over a large surface in the clamped stack of registration base, pallet, and workpiece, to maintain overall stack height accuracy.